The present invention relates to an electron source, and more particularly concerns an electron-source array which is applied to displays, fluorescent display tubes, lamps, electron guns, etc., and which can be driven based on the X-Y matrix, and a manufacturing method thereof as well as a driving method for such an electron-source array.
In recent years, it has been expected that field emission displays (FED) can be applied to self-emission type flat panel displays, and studies and developments have been extensively made on electron emitting type electron sources. With respect to the electron source used for FEDs, a pyramid-type metal electron source, disclosed by C. A. Spindt et al. as shown in FIG. 35 (U.S. Pat. No. 3,665,241), has been well known.
As illustrated in FIG. 35, the electron source has a construction in which: a cathode electrode 113, a gate insulation layer 114 and a gate electrode 115 are successively stacked on a substrate 112 and a conic shape metal emitter (electron source) 116 electrically connected to the cathode electrode 113 is placed into a through hole 114a reaching the cathode electrode 13, formed in the gate insulation layer 114.
In the above-mentioned electron source, however, although the conic shape metal emitter 116, which is an electron source, is made of a high-melting-point metal material, there have been serious problems relating to the tip-diameter control, uniformity control and reliability of the electron source (metal emitter 116).
Moreover, in 1991, a carbon nanotube was discovered by Iijima, et al. (Nature, 354, 56, 1991). This carbon nanotube has an arrangement in which a graphite layer, rolled into a cylinder shape, is allowed to have a nest shape, and its tip diameter is approximately 10 nm; thus, since this is superior in oxidation resistant property and ion-impact resistant property, this is considered to form a material having superior properties for use as the electron source.
In fact, in 1995, research groups of R. E. Smalley et al. (Science, 269, 1550, 1995) and W. A. de Heer et al. (Science, 270, 1179, 1995) reported electric field discharging experiments from carbon nanotubes. In the electric field discharging experiments of this type, a carbon nanotube is placed on a metal electrode as a cast film and a metal plate mesh is used as a lead-out electrode so that electrons are collected onto an anode that is an opposing electrode.
With respect to an electron source using such a carbon nanotube, for example, Japanese Laid-Open Patent Application No. 162383/1999 (Tokukaihei 11-162383 (published on Jun. 18, 1999)) (hereinafter, referred to as reference 1) has disclosed a technique in which a carbon nanotube in the form of paste is formed on a substrate by a printing method so as to manufacture a plane display.
As illustrated in FIG. 36, in the electron source disclosed in reference 1, a cathode electrode 113 is formed on a substrate 112 as a metal electrode, an insulation layer 121 having contact holes 120 is formed on the cathode electrode 113, ribs 122 are formed on the insulation layer 121 in the form of lines in a manner so as to avoid the contact holes 120, a gate insulation layer 114 is formed on the ribs 112, and a carbon nanotube film 123 is formed so as to cover areas having the contact holes 120 of the insulation layer 121 as a paste film, with an anode electrode 124 being located so as to oppose the gate insulation layer 114 with a space in between.
Moreover, Japanese Laid-Open Patent Application No. 12124/1998 (Tokukaihei 10-12124 (published on Jan. 16, 1998)) (hereinafter, referred to as reference 2) discloses an electron source in which, as illustrated in FIG. 37, an alumina layer 118 is placed on a substrate 112 made of glass with an aluminum layer 117 interpolated in between, and in which pores reaching the aluminum layer 117 are formed in the alumina layer 118. Carbon nanotubes 119, which have grown as metal catalyst starting points, are placed in the respective pores formed in the alumina layer 118 so that the carbon nanotubes 119 to which power is supplied through the aluminum layer 117 are allowed to function as electron sources.
Therefore, conventionally, with respect to the electron source, it has been known that the time-wise stability of the current intensity is improved by allowing the carbon nanotubes to selectively grow in the pores in the metal and regularly arranging the carbon nanotubes.
However, in the conventional electron source using carbon nanotubes as shown in reference 1, as illustrated in FIG. 36, only a paste film is two-dimensionally formed on the cathode electrode 113 that is a metal electrode;
consequently, it is impossible to control a number of electron-emitting points located on the surface of the paste film. For this reason, it is difficult to ensure uniformity between respective pixels that constitute a display.
Moreover, the carbon nanotube film 123, formed on the cathode electrode 113 that is a metal electrode, is a plane paste film, with the result that it becomes difficult to control the electron emitting points, and electron discharge takes place randomly on the paste film that forms the discharging section, with the result that it becomes very difficult to assemble this film into a device.
Moreover, as illustrated in FIG. 37, in reference 2, the division of the electron source is achieved by allowing the carbon nanotubes to selectively grow in the pores in the metal; however, in order to separate the electron source, the anodic oxidation film and metal forming a pre-oxide have to be removed up to the supporting substrate, resulting in a difficulty in carrying out X-Y matrix driving required for a display.
Moreover, since the temperature of this process also reaches 1000xc2x0 C., this process cannot be applied if there is metal remaining as an unoxidized portion, in particular, if there is low-melting-point metal, such as aluminum, remaining as such.
The objective of the present invention is to provide an electron-source array which enables X-Y matrix driving that is indispensable for achieving a display and also has a construction that is suitable for practical use in terms of processes, and a manufacturing method for such an electron-source array.
In order to achieve the above-mentioned objective, the electron-source array of the present invention, which is provided with cathode electrodes placed on an insulation substrate in the form of lines and gate electrodes that are placed face to face with the cathode electrodes with the insulation film being interpolated in between, is characterized in that the cathode electrodes and the gate electrodes are arranged so as to orthogonally intersect each other with a pore being formed at an intersecting portion between each cathode electrode and each gate electrode in a manner so as to penetrate the insulation film, and in that the pore is filled with a conductive material or a semiconductive material with the material being electrically connected to the corresponding cathode electrode, and is formed in a manner so as to separate from the gate electrodes with a space in between.
Thus, since the gate electrode is placed in a manner so as to orthogonally intersect the cathode electrode, it is possible to provide a construction that enables the X-Y matrix driving that is indispensable for achieving a display.
Moreover, in order to achieve the above-mentioned objective, the electron-source array of the present invention, which is provided with cathode electrodes placed on an insulation substrate in the form of lines, and gate electrodes that are placed face to face therewith with the insulation film being interpolated in between, may be arranged so that the gate electrodes are placed in a manner so as to surround each of electron emitting areas that are developed planarly on the cathode electrodes, and so that electron emitting sections, which form a plurality of separated divisions on each cathode electrode, are formed within the electron emitting area, with each electron emitting section being constituted by an aggregate mainly formed by an electron emitting material having a fine size.
In other words, in the case when the electron emitting section is constituted by an aggregate mainly formed by an electron emitting material having a fine size (for example, carbon-based materials, such as carbon nanotube, carbon fibers, graphite, diamond and diamond-like carbon), the electron emitting section, formed on each cathode electrode surrounded by the gate electrodes, may be formed separately into a plurality of divisions within the electron emitting area.
In the case when the electron emitting section is constituted by an aggregate of an electron emitting material having a fine size and the electron emitting section, formed on each cathode electrode, is developed in a film shape, it is difficult to control the electron emitting points, and the electron emission takes place randomly within the film face, which is different from the case where the electron emitting sections are formed regularly in the pores. However, when the electron emitting section is separated into a plurality of divisions within the electron emitting area, the electron emitting points are dispersed so that the operation of the electron-source array can be stabilized and uniformed.
Moreover, the manufacturing method of another electron-source array of the present invention comprises the steps of: patterning cathode electrodes on the surface of a substrate, patterning an insulation film on the cathode electrodes and the substrate, patterning a ballast resistance layer, patterning a conductive layer on the ballast resistance layer, patterning a gate insulation film, patterning a pre-oxide that forms an insulation film having the pores on the ballast resistance layer, forming pores in the pre-oxide while converting it into an insulation film, further patterning the insulation film, filling the pores with an electron emitting material, patterning a first gate electrodes, and patterning a second gate electrodes.
Among the manufacturing processes, in the process for forming pores in the pre-oxide after the process for patterning the pre-oxide that forms an insulation film having pores, the present invention features that an anodic oxidation method is adopted by using the cathode electrodes as the corresponding electrodes. In other words, the present invention features that the anodic oxidation method is used as a method for forming the insulation film having pores, and that a method for removing a barrier layer formed through the anodic oxidation and for allowing the pores to penetrate is provided as a method for dissolving the barrier layer by applying a voltage reversed to that of the cathode oxidizing method. In this case, a material that is resistant to the cathode oxidizing solvent is used as the ballast resistance layer; thus, it is possible to use the ballast resistance layer as a stopper layer for protecting the cathode electrodes, and for completely converting the pre-oxide into the insulation film.